Remarks on the Number of Generations of The European Corn Borer in America

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Abstract
In this paper the theory that there are at present two geographical races of the European corn borer, Pyrausta nubilalis, in America is discussed. Larvae transferred from New York to Massachusetts in 1920 have for four years maintained a single annual generation while larvae from Massachusetts that had a single generation during 1920 have been reared under the same conditions and have had a partial second generation each year. The fact that individuals in the infested area about Lake Erie are practically all large and well nourished while in New England many larvae enter hibernation in the fall half starved and from a third to a half smaller than normal larvae suggests the theory that the infestation about Lake Erie will be more dependable from year to year. This has proved to be the case during 1923 and 1924 when the New England infestation has decreased and the infestatton about Lake Erie has increased both as to spread and in intensity of infestation. There is also considered the theory that the New England infestation may be reverting to a single generation habit by a process of natural selection in view of an environment that will not support two annual generations.

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